<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  
  </style>
</head>
<body>
  <div id="app">
    <div :class="a">div</div>
    <div :class="[a,b,'box3',1>2?'a':'b']"></div>
    <div :class="{isActive:c}"></div>
    <div :class="{isActive:1!=2}"></div>
    <div :class="[a,b,'box3',{isActive:c},1>2?'a':'b']"></div>
  </div>
  <script src="./vue.js"></script>
  <script>
    /* var a = 'box';
    var b= 'box2';
    var arr = [a,b,'box3',1>2?'a':'b']
    console.log(arr) */
    const vm = new Vue({
      el: '#app',
      data: {
        a:'box',
        b: 'box2',
        c: true
      }
    })
  </script>
</body>
</html>